In the fabrication of semiconductor based devices (e.g. integrated circuits or flat panel displays), layers of material may alternately be deposited onto and etched from a substrate surface (e.g., the semiconductor wafer or the glass panel). As is well known in the art, the etching of the deposited layer(s) may be accomplished by a variety of techniques, including plasma-enhanced etching. In plasma-enhanced etching, the actual etching of the substrate takes place inside a plasma processing chamber. During the etching process, a plasma is formed from a suitable etchant source gas to etch areas of the workpiece that are unprotected by the etch mask, leaving behind the desired pattern.
During plasma etching of a substrate, etch byproduct, which is made of polymers formed by photoresist or etched material layer with etching chemistry, is mainly deposited on the peripheral chamber hardware. The deposited byproduct accumulates with subsequent substrate etching. To improve device yield of substrate manufacturing, it is important to maintain a reproducible chamber, which can be achieved by performing a chamber cleaning process periodically after one or more substrate has been etched. Typically, chamber cleaning is performed after etching every substrate.
Capacitively coupled vacuum plasma systems are frequently employed to etch dielectric material from a semiconductor substrate. The capacitive systems have the advantages of causing low plasma damage and having higher selectivity to the underlayer and photoresist layer. However, when a capacitively coupled plasma is used to clean the chamber after substrate etching, the capacitively coupled plasma, which has relatively high ion energy, would bombard the exposed electrostatic chuck. The electrostatic chuck is used to support the substrate during substrate etching, and bombarding the exposed electrostatic chuck results in electrostatic chuck lifetime degradation and particle generation. In addition, the capacitively coupled plasma generated by the top and bottom electrodes in the chamber is mainly concentrated in the center region above the electrostatic chuck and is not effective in cleaning the peripheral chamber hardware. In order to fully clean the peripheral chamber hardware, extended cleaning time is needed, which impacts the manufacturing throughput. In current capacitively coupled plasma reactors, the chamber clean after processing (or etching) each substrate is generally optimized within the constraints mentioned above.
In view of the foregoing, there is a need for a method and apparatus that provides an improved chamber cleaning mechanism to increase electrostatic chuck lifetime, to improve substrate yield, and to increase manufacturing throughput.